patio drainage

[sm_jamieson]

When I do the patio I want to drain it properly with a strip of linear drai n against the house (main garden on level with DPC). Its a combined sewer/r ainwater setup here. I have a bottle gully under the outside tap, which I c an replace with the linear drain gully/connector box, but this does not con tain a trap. So I need to add a roddable trap hopefully tight against the d rain connector box to avoid too many "things" cut into the patio paving (I already will have 2 manhole inset boxes). Can anyone suggest a suitable roddable trap ?

I like the look of the slot drains, but it seems the only way you could unb lock them is to make them roddable from the ends whereas the linear drain g rating comes off.

By the way, when searching for this I came across the bad advice to connect the linear drain to the extra connection of a back inlet bottle trap. Of c ourse the trap is only between the top inlet and the underground connection s - there is a air path between the front and back connections around the c ylindrical core of the trap !

Cheers, Simon.

[sm_jamieson]

ain against the house (main garden on level with DPC). Its a combined sewer /rainwater setup here. I have a bottle gully under the outside tap, which I can replace with the linear drain gully/connector box, but this does not c ontain a trap. So I need to add a roddable trap hopefully tight against the drain connector box to avoid too many "things" cut into the patio paving ( I already will have 2 manhole inset boxes).

nblock them is to make them roddable from the ends whereas the linear drain grating comes off.

ct the linear drain to the extra connection of a back inlet bottle trap. Of course the trap is only between the top inlet and the underground connecti ons - there is a air path between the front and back connections around the cylindrical core of the trap !

There is trapped connector box available for the Floplast system. However I doubt it is roddable, unless you can get into the trap from inside the cha nnel. Is it a requirement for rainwater drainage into a combined sewer to be rodd able ? I suppose in theory it is roddable the other way from the inspection chambe r a few metres away.

Simon.

[Dave Baker]

My patio has about 10 ft of linear drain running down the middle with a grating over the top. The patio slopes both ways, down from the house and down from the lawn so the grating is the lowest point. I cleared out the crap in it for the first time last week and it's quite interesting how it was designed. The 4" diameter semi circular U gulley under the grating is at a higher level than the 4" diameter full circular drain pipe it runs into so they only overlap by about an inch at the top which stops anything big getting into the main drain and blocking it. The gulley was full to the top with silt, twigs, leaves and a thriving colony of worms which went into the borders to help fertilise the soil but once I'd trowelled all that out the main drain was clear as a bell. I thought it was quite cunning and you might want to employ it.

[harryagain]

I like the look of the slot drains, but it seems the only way you could unblock them is to make them roddable from the ends whereas the linear drain grating comes off.

By the way, when searching for this I came across the bad advice to connect the linear drain to the extra connection of a back inlet bottle trap. Of course the trap is only between the top inlet and the underground connections - there is a air path between the front and back connections around the cylindrical core of the trap !

They soon block up with leaves etc. You are better to get one with liftable grids. They have one in screwfix that has an intercptor as part of the package

[Brian Gaff]

Maybe the person owning that had no sense of smell? Brian

[Rick Hughes]

is this a product or the way some things have been connected ... not following this easily. care to explain further.

[Dave Baker]

Just the way they've been laid out. Clay semi circular gulley under the grating at ground level. Abuts to, but does not connect to obviously, circular drain pipe laid a couple of inches lower so the top of the drain pipe is about 1 inch above the bottom of the gulley. Not sure how I can explain it better.

[sm_jamieson]

ain against the house (main garden on level with DPC). Its a combined sewer /rainwater setup here. I have a bottle gully under the outside tap, which I can replace with the linear drain gully/connector box, but this does not c ontain a trap. So I need to add a roddable trap hopefully tight against the drain connector box to avoid too many "things" cut into the patio paving ( I already will have 2 manhole inset boxes).

nblock them is to make them roddable from the ends whereas the linear drain grating comes off.

ct the linear drain to the extra connection of a back inlet bottle trap. Of course the trap is only between the top inlet and the underground connecti ons - there is a air path between the front and back connections around the cylindrical core of the trap !

To be honest I was originally going to lay out the patio so the water ran t o the two existing gullies, letting the house wall act as a barrier to guid e the water. Its a cavity wall whose outer leaf is solid blue engineering b ricks and strong mortar, and many patios are done just this way without pro blems.

I have a side path about 1 metre wide that in theory could have a linear dr ain but that just seems silly. On that side I'm sure grading the path towar ds the house and towards the trap on that corner will be fine.

Simon.

[Andrew Gabriel]

Something else to consider - if you have a hard surface right up to the house wall, you will get rain splashing back up the wall, and this can damage the bricks and mortar over time through water penetration and frost damage (depending on absorbency of the bricks).

A 6" gap filled with small stones or soft foliage (such as grass) to absorb the impact of the rain drops will prevent this. Sometimes, this is made into a french drain by actually making a gully there and filling it with fine stones, but you want to make sure it drains well rather than turning into a moat against the wall.

[sm_jamieson]

Well the recommended 150mm below DPC for hard surfaces is specified to reduce the rain splashback. The other trick I have seen is to angle the surface against the wall for a short distance to encourage splashing away. Simon.

[Andrew Gabriel]

That doesn't reduce splashback - it just helps prevent it getting above the DPC. Won't stop the bricks spalling below the DPC.